The IEEE 802.11 wireless standards define a frame exchange, between an initiator (e.g., mobile) and a responder (e.g., access point), from which time-of-flight (ToF) can be determined. The standards typically assume that the initiator is available to receive a response from the responder for the entire time after the initiator makes its request. However, the ToF calculations can take many milliseconds to accomplish. This can force the initiator to dwell on the requested channel until the response arrives, thus preventing the initiator from accomplishing any other tasks. For example, instead of being able to return to a serving channel (if not the same as the current ToF exchange channel), perform a power save function, and/or perform additional exchanges with the responder on a different channel, the initiator has to dwell on the ToF channel until a response is received.
The dwell problem can be worse when the initiator performs a trilateration for increased location accuracy. In such a scenario, the time the initiator dwells away from its serving channel can be multiplied by the number of dwell times encountered for each ToF calculation.
Thus there are general needs for improved ToF determination methods. There are also general needs for reducing initiator dwell time.